1) Field of the Invention
The present invention relates to a technology that makes it possible to regulate a temperature of a localized portion of a microchemical chip.
2) Description of the Related Art
A thermoelectric element includes a plurality of thermocouples that transfer thermal energy into electric energy, and vice versa. A thermocouple is formed with a p-type and an n-type thermoelectric semiconductors of substantially the same lengths, and the p-type and the n-type thermoelectric semiconductors are connected with each other end to end.
In a typical thermoelectric element, more than one thermocouples are arranged in such a manner that the p-type and the n-type thermoelectric semiconductors alternate and the thermocouples are electrically connected to each other in series. The thermoelectric element generates voltage due to Seebeck effect when a temperature difference occurs between its two ends. On the other hand, absorption of heat occurs at one end and radiation of heat occurs at other end of the thermoelectric element due to Peltier effect when a direct current is applied to it. In other words, the thermoelectric element shows a reversible effect.
Because the thermoelectric elements show the reversible effect, they are advantageously used in thermoelectric transducers. Precisely, since surface temperatures of the ends of the thermoelectric element can be precisely controlled by controlling an amount and a direction of an electric current flowing through it, it can be advantageously used as a temperature regulator.
A microchemical chip is a chip used for performing a chemical process and studying the process. The chemical reaction is performed at a portion, i.e. a chemical reaction section, of the microchemical chip. The chemical reaction section can be on the surface or it can be inside the microchemical chip. Several kinds of microchemical chips are known. Chips for DNA analysis (DNA chips), chips for protein analysis, micro TASs (Total Analysis System), Lab-on-a-chips, and microreactor chips are just a few example of the microchemical chips.
Various kinds of chemical processes can be carried out in chemical reaction sections. Mixing, reaction, extraction, separation, and condensation are few examples of such chemical processes. It is necessary to set a temperature at an optimal condition for each of the processes, for example, to speed up a reaction, to stabilize or activate a system in the reaction, or to enhance efficiency of the reaction.
If there are more than one chemical reaction sections in a microchemical chip, it becomes necessary to take measures to avoid transmission of heat from one chemical reaction section to other chemical reaction sections to keep the optimal temperature for each chemical reaction section. Therefore, a structure that enables to locally control the temperature at each of the chemical reaction section is required. A microchemical chip that has such a structure, i.e., a structure that enables local temperature adjustment, has been disclosed in International Publication No. 0048724.
FIG. 17 is a schematic of a microchemical chip that is disclosed in the above patent literature. A thermoelectric element 103 is arranged right under a chemical reaction section 102 in a microchemical chip 101. It is possible to speed up the reaction in the chemical reaction section 102 by heating or cooling the chemical reaction section 102, or by adjusting a temperature at the chemical reaction section 102 with the thermoelectric element 103.
However, in the conventional technology disclosed in the above patent literature, the thermoelectric element 103 is not connected to a heat exchangeable object such as a heat sink. This causes a problem in which heat tends to accumulate in the thermoelectric element 103 when the temperature at the chemical reaction section 102 is adjusted by heating or cooling with the thermoelectric element 102 connected to the microchemical chip 101. In addition, in the above patent literature, none of a specific structure for connecting the microchemical chip 101 and the thermoelectric element 103 is disclosed. Therefore, it is difficult to connect the microchemical chip 101 and the thermoelectric element 103 while keeping sufficient heat conductivity. This causes inefficiency in the temperature adjustment at the chemical reaction section 102. Furthermore, none of a specific structure of a control apparatus to control the temperature is disclosed. Therefore, it is impossible to actually carry out the temperature adjustment by heating or cooling.